tripler & PA affect frequency deviation?
This problem disturb me for so long during my developing a RF module for 2.4GHz wireless project. I don't think I fool mother nature. What I discripted is true. I only want discuss about this strange phenomenon which I met and share my experience because I have now resolve it.
1. If the 800Mhz is input without modulation(CW), the output frequency is no problem, i.e. 3 times the input.
2. If not connected to the match net to tripler, the deviation of every channels(low, middle, high band) is correct. This means that the VCO sensitivity over all frequecy is no problem. And I surely affirm that the tripler and PA both have some degree affection to the deviation, as well as the shield cover location.
3. There is no oscillation because of the sheild cover location.
4. I think there are no noise coupled to PLL's offchip loop filter for the enough distance from tripler and GND protect.
At last, I can only conculude that the only propable reason is the reflect signal from the tripler. I resolved the problem through the following efforts.
1. Redesign the tripler with higher convertion gain to replace the previous tripler with the aid of ADS.
2. Use ceramic filer to replace the previous microstrip inter finger filter, which with less insert loss and more accurate 50ohm in/out impedance for convenience of following match design.
3. Shut a capacitor at the receiver input match part after the T/R switch.
Now, everything is OK. Hope the above discussion will helpful for all friends. Lucky!!